1. Field of the Invention
This invention relates to brake head assemblies for using in brake beams of railway cars, and more particularly to a joint for pivotally joining a brake head to a brake beam of a railway car by which it is achieved an adequate force transference along the brake shoe and an adequate contact between the brake shoes and the railway car bogie wheels.
2. Description of the Related Art
Most railroad freight cars, use a mechanism called brake rigging. On the car body, there is an air brake system which provides air to the brake cylinder, which in turn, supplies a mechanical force through a system of rods and driving levers to a connection on the standard freight car trucks located at each end of the car. At this point, the force is applied to a truck driving lever system, usually consisting of two driving levers and a connecting rod. The driving levers move brake beams, which apply force to the treads of the wheels through renewable friction blocks or brake shoes, retarding the rotation of the wheels.
The conventional brake rigging includes two brake beams, at least one brake cylinder assembly and a driving lever or linkage assembly so connected between the brake beams and cylinder assembly that actuation of the cylinder assembly moves the brake beams away from one another and into braking engagement with treads of wheels of a railway vehicle truck.
There are many brake beam configurations which may be used with the above referred general type of brake rigging, but the most commonly used brake beam configuration comprises: a compression member, a generally xe2x80x9cVxe2x80x9d shaped tension member having its ends coupled to the ends of the compression member, a brake head linked to the each end of the compression and/or tension members, each comprising a brake shoe carrier having a brake shoe, two end extensions, each linked at each end of the tension and/or compression member, or hanging means, by which the brake beam is coupled to the bogie of a railway car, and a fulcrum assembled to the compression member and tension member, so that the fulcrum remains between the tension and compression members.
Normally, the brake heads are fixedly linked to the brake beam by means of bolts passing through perforations located at the ends of the brake beam and through perforations located at the brake heads. Also, the brake heads may be linked to a brake beam by welding the brake shoe carriers directly to the ends of the brake beam.
The looseness between the extensions of the brake beam and its guidesxe2x80x94which is necessary in order to compensate for the movements of the truck components when it""s in operationxe2x80x94, causes the brake beam to hang from the truck, so that its position does not point to the center of the wheel. Furthermore, during the braking operation, due to existent rigid joints between the extensions of the brake beam and its truck guides, between the brake heads and the wheels during the braking operation and between the brake head and the brake beam, the forces applied to the brake head are not transmitted in an uniform way along the brake shoe, thus producing a non-uniform and incomplete wear of the useful material of the brake shoes, which is a waste of useful material that could be properly used, and therefore, the maintenance team is forced to frequently change the brake shoe material which is a waste of time and money.
In extreme cases, the material of the brake shoe is so worn at some points, that the metal of the brake shoe carrier comes in direct contact with the correspondent bogie wheel, damaging the brake shoe carrier as well as the wheel.
Considering the above referred problems, applicants developed a joint for pivotally joining a brake head to a brake beam which pivotally joints the brake head to the brake beam in order to allow the brake head to modify its radial direction with respect to the wheel, thus allowing the brake shoe to adapt to the wheel contour and achieving an adequate force distribution along the brake shoe.
Applicants joint for pivotally joining a brake head to a brake beam comprises: brake beam linking means, fixedly linked to a brake beam or linked with a controlled degree of rotational freedom to a brake beam, and including pivoting retaining means for pivotally retain a brake head, and brake head pivotal linking means located at the brake head for pivotally retain the brake head to the pivoting retaining means of the brake beam linking means.
With applicants pivotal joint, all the useful material of the brake shoe is totally used, thus avoiding frequent changes of the brake shoe material, which help to achieve great money saves in view of the high maintenance costs caused by the frequent changes, and avoid the waste of useful brake shoe material that still could be used if the thickness of the remaining material were uniform.
It is therefore a main object of the present invention, to provide a joint for pivotally joining a brake head to a brake beam.
It is also a main object of the present invention to provide a joint for pivotally joining a brake head to a brake beam, which allows the brake head to modify its radial direction with respect to the beam by self-adjusting with respect to the wheel.
It is also a main object of the present invention to provide a joint for pivotally joining a brake head to a brake beam, by which it is achieved an uniform force distribution along the brake shoe, thus allowing the brake shoe material of the brake head to adapt to the wheel contour as the material of the brake shoe is worn.
It is still another object of the present invention to provide a joint for pivotally joining a brake head to a brake beam, by which all the useful material of the brake shoe is totally used, thus avoiding frequent changes of the brake shoe material.
It is still another object of the present invention to provide a joint for pivotally joining a brake head to a brake beam, by which it is achieved an uniform and complete wear of all the brake shoe material.
These and other objects and advantages of the joint for pivotally joining a brake head to a brake beam of the present invention will become apparent to those persons having an ordinary skill in the art, from the following detailed description of the embodiments of the invention, which will be made with reference to the accompanying drawings.